Magnesium compounds, anhydrous

Add 4 0 g. (4 0 ml.) of pure anihne dropwise to a cold solution of ethyl magnesium bromide (or iodide) prepared from 1 Og. of magnesium, 5 0 g. (3-5 ml.) of ethyl bromide (or the equivalent quantity of ethyl iodide), and 30 ml. of pure, sodium-dried ether. When the vigorous evolution of ethane has ceased, introduce 0 02 mol of the ester in 10 ml. of anhydrous ether, and warm the mixture on a water bath for 10 minutes cool. Add dilute hydrochloric acid to dissolve the magnesium compounds and excess of aniline. Separate the ethereal layer, dry it with anhydrous magnesium sulphate and evaporate the ether. Recrystallise the residual anihde, which is obtained in almost quantitative yield, from dilute alcohol or other suitable solvent. 

Anhydrous diethyl ether is the customary solvent used when preparing organo magnesium compounds Sometimes the reaction does not begin readily but once started It IS exothermic and maintains the temperature of the reaction mixture at the boiling point of diethyl ether (35°C)... 

Oddo reported that the organomagnesium derivatives of p3Trole, indole, skatole, and carbazole could be prepared in a single operation by mixing the parent heterocyclic compound with an alkyl halide and magnesium in anhydrous ether.The product formed was reported to be the same as that obtained by the more conventional procedure. However, this approach to the synthesis of the indole Grignard reagents does not seem to have been exploited in subsequent work. 

To the solution of the magnesium compound so obtained the following solution is added dropwise, with stirring so as to maintain a slight reflux of ether 1,2-dibromo-2-(2-chloro)-ethoxyethane 550 g. Anhydrous ether 300 ml. 

Among the metallic reducing systems [42a, b] which have been suggested are magnesium with anhydrous methanol [42a], and an alloy of sodium and lead (sold as Drynap ) in ethanol [43, 44], In the case of the magnesium-methanol reduction, the product mixture usually contains azoxy-, azo-, hydrazo-, amino-, and hydroxylamine products, although approximately 75% of the product consists of a mixture of azoxy and azo compounds. The Dry-nap reduction also seems to lead frequently to mixtures of azoxy and azo compounds. 

The bimolecular reduction of aromatic nitro compounds, depending on reaction conditions, may produce azoxy compounds, azo compounds, hydrazo compounds (1,2-diarylhydrazines), benzidines, or amines. Whereas the reduction with zinc and sodium hydroxide leads to azo compounds, zinc and acetic acid/acetic anhydride produces azoxy compounds. Other reducing agents suggested are stannous chloride, magnesium with anhydrous methanol, a sodium-lead alloy in ethanol, thallium in ethanol, and sodium arsenite. 

Magnesium compounds hydrate readily, and anhydrous magnesium halides form addition compounds with aldehydes, ketones and ethers, which are structurally similar to those of Be. Otherwise its complexes are few and unstable. 

Methylcyclopentadienylpotassium or -sodium does not form Mg(C5H4Me)2 by reaction with anhydr Mg salts in EtjO or THE. Nevertheless, a range of bis(dienyl)-magnesium compounds MgRj is formed by reaction of 2 1 KR with MgBr2 in THE . When R = RCH=CR CR"=CR " CHj (R, R, R", R" being various combinations of H... 

To the magnesium compound from 50 grams of 1 4-dibromobutane m 200 c.c. of anhydrous ether, 40 grams of phenyldichlorostibine dissolved in S volumes of dry ether are slowly added, the mixture being well cooled and stirred, and the operation conducted in an inert gas. Fractionation of the resulting product after decomposition gives 15 grams of the stibme, B.pt. 156° to 158° C. at 20 to 22 mm., np 1-6313 and m-no 0 02737 at 23° C. 

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